OP -- is your point here to test a circuit, or as a (semi-)permanent supply for a "production" project? If it's for testing, I would go the route of the ATX PSU. If you're looking for something permanent, I would choose something else.

Have you ever built your own? Is that an option? I use a linear AC-DC conversion stage with various E-I, toroidal, or PCB-mount transformers, then linear regulators for low-current (less than 500mA) rails. I'll use switching regulators for 500mA to 5A. Often when using higher-current devices, regulation isn't as important, so a rectified DC output with adequate filtering is good enough.